# File lib/RMagick.rb, line 1034
    def set_cf(cfid)
        if length == 0
            @scene = nil
            return
        # Don't bother looking for current image
        elsif @scene == nil || @scene >= length
            @scene = length - 1
            return
        elsif cfid != nil
            each_with_index do |f,i|
                if f.__id__ == cfid
                    @scene = i
                    return
                end
            end
        end
        @scene = length - 1
    end